1. Field of the Invention
The present invention relates generally to a system for controlling timings such as fuel injection timing and ignition timing on a cylinder-by-cylinder basis in an internal combustion engine. More particularly, the present invention is concerned with a cylinder identifying system for an internal combustion engine for detecting reference crank angle positions (hereinafter also referred to simply as the reference positions) for the cylinders, respectively, on the basis of crank angle pulse signals (reference position signals) and cylinder identifying pulse signals for the purpose of controlling the timings such as mentioned above. In particular, the present invention concerns a cylinder identifying system which is capable of detecting with high accuracy and reliability the reference position for each of the cylinders independently of operation states of the internal combustion engine by effectuating a reference position detecting procedure of performance specifications optimal for the engine operation state by selecting the reference position detecting procedure of the optimal performance specifications from those prepared separately for the engine operations in a low rotation speed range and a high rotation speed range, respectively.
2. Description of Related Art
In general, in the internal combustion engine for an internal combustion engine for a motor vehicle or the like, it is required to control optimally the fuel injection timing and the ignition timing in conformance with the operating conditions or operation states of the internal combustion engine. For satisfying such requirement, signal generating means including respective sensors are provided in association with rotatable shafts (a crank shaft and a cam shaft) of the internal combustion engine with a view to generating reference position signals indicating the reference positions, respectively, on a cylinder-by-cylinder basis and cylinder identifying pulse signals for identifying discriminatively the individual or specific cylinders, respectively. On the basis of these signals, discriminative identification of the engine cylinders is carried out.
As the conventional cylinder identifying system for the internal combustion engine known heretofore, there may be mentioned the one disclosed, for example, in Japanese Patent Application Laid-Open Publication No. 317930/2000.
The reference position detecting means employed in the above-mentioned conventional cylinder identifying system for the internal combustion engine is so arranged as to generate a number of equidistant pulse signals (i.e., pulses having equal inter-pulse intervals) as the crank angle pulse signals while generating a plurality of nonequidistant pulse signals corresponding, respectively, to the reference positions admixedly in the equidistant crank angle pulse signals, wherein the reference positions indicated by the nonequidistant pulse signals admixed in the crank angle pulse signals are detected on the basis of the changes of the period ratios TR(n) among the individual pulses of the crank angle pulse signals and the nonequidistant pulse signals.
More specifically, the period ratio TR(n) is determined from the periods T(nxe2x88x921) and Tn of a preceding crank angle pulse signal and a current crank angle pulse signal Tn in accordance with
TR(n)=Tn/T(nxe2x88x921)
Subsequently, the period ratio TR(n) as determined is compared with a predetermined value Kr. At the time point when the comparison shows that TR(n)xe2x89xa7Kr, the reference position can then be discriminatively recognized or identified.
On the basis of the reference positions detected for the cylinders in this manner, the fuel injection timings and the ignition timings can be controlled for the individual cylinders with high accuracy.
However, the relatively simple reference position detecting means such as described above is disadvantageous in that when the rotation period of the engine changes abruptly as encountered in the engine cranking operation or upon combustion stroke of the engine cylinder, the period of the crank angle pulse signal which is to remain constant will change, resulting in erroneous detection of the reference position. In other words, in the situations such as mentioned above, it becomes impossible to detect the reference position with reasonable accuracy and reliability, which incurs erroneous control of the individual cylinders, giving rise to a problem.
In order to detect the reference position with high accuracy and reliability while avoiding the erroneous detection or identification of the reference position and the engine cylinders, there is demanded very complicate arithmetic operation procedure which can certainly be executed during a cranking operation in a low rotation speed range. However, in a high rotation speed range where the number of interrupt processings issued for a microcomputer constituting a major part of an engine control unit increases, there will arise such undesirable situation that the arithmetic operation procedure for detecting the reference position can not timely be executed.
To say in another way, when the detection procedure of simple performance specifications is employed for detecting the reference position from the crank angle pulse signals in the conventional apparatus, detection of the reference position with high accuracy is rendered impossible in the low rotation range where the period of the crank angle pulse signal changes remarkably.
On the other hand, when the detection procedure of complicate performance specifications is resorted to, the arithmetic operation processing as involved can not timely be executed but may be skipped, to another problem.
As is apparent from the foregoing, the conventional cylinder identifying system for the internal combustion engine suffers a problem that when a simple reference position detecting means is employed, the reference positions of the individual cylinders will be erroneously detected or identified upon change of the rotation period of the internal combustion engine, making it impossible to realize detection of the reference position with reasonable accuracy.
On the other hand, in the case where complicate arithmetic operation processing procedure is adopted in an effort to enhance the accuracy of detection of the reference position, the number of the interrupt processings issued to the microcomputer or ECU will become too large to be executed by the microcomputer in a high rotation speed range, giving rise to a problem that the reference position can not be detected with desired accuracy and reliability.
In the light of the state of the art described above, it is an object of the present invention to provide a cylinder identifying system for the internal combustion engine which is capable of detecting the reference positions on a cylinder-by-cylinder basis with a high accuracy and an enhanced reliability independently of different rotation ranges and change of the engine rotation speed by providing performance specifications for low and high rotation speed ranges, respectively, in executing the reference position detecting processing procedure.
In view of the above and other objects which will become apparent as the description proceeds, there is provided according to a general aspect of the present invention a cylinder identifying system for an internal combustion engine.
The cylinder identifying system includes a crank angle signal generating means for generating a plurality of crank angle pulse signals in correspondence to rotation angles of a crank shaft of the internal combustion engine, a cylinder identifying signal generating means for generating cylinder identifying pulse signals corresponding to cylinders, respectively, of the internal combustion engine during rotation of a cam shaft arranged to rotate at a ratio of 1/2 relative to the rotation of the crank shaft, a reference position detecting means for detecting reference positions on the basis of the crank angle pulse signals, a cylinder identifying interval setting means for setting cylinder identifying intervals with reference to the reference positions, a cylinder identifying means for identifying the individual cylinders on the basis of the cylinder identifying pulse signals in the cylinder identifying intervals, and an operation state detecting means for detecting operation state of the internal combustion engine in a low rotation speed range and a high rotation speed range of the internal combustion engine.
The reference position detecting means mentioned above is composed of a first detection processing means for effectuating a processing procedure of the performance specifications corresponding to the low rotation speed range, and a second detection processing means for effectuating a processing procedure of first performance specifications corresponding to the high rotation speed range. Operations of the first detection processing means and the second detection processing means are changed over with each other in dependence on the operation states of the internal combustion engine.
By virtue of the arrangement of the cylinder identifying system for the internal combustion engine described above, the reference positions can be detected on a cylinder-by-cylinder basis with a high accuracy and an enhanced reliability regardless of the different rotation ranges and change of the engine rotation speed.
In a preferred mode for carrying out the invention, the operation state detecting means may be so designed as to detect the rotation number of the internal combustion engine as an engine rotation number while the reference position detecting means may be designed to change over the first reference position detecting means and the second reference position detecting means with each other in dependence on the engine rotation number.
With the arrangement of the cylinder identifying system described above, it is possible to detect the reference positions on a cylinder-by-cylinder basis with high accuracy and reliability without incurring any appreciable increase in the cost.
In another preferred mode for carrying out the invention, the operation state detecting means may be so designed as to detect a cranking state of the internal combustion engine while the reference position detecting means may be designed to change over the first reference position detecting means and the second reference position detecting means with each other in dependence on presence or absence of the cranking state.
With the arrangement of the cylinder identifying system described above, the reference position can be detected for each of the individual cylinders with enhanced accuracy and reliability while mitigating overhead involved in the arithmetic operation.
The above and other objects, features and attendant advantages of the present invention will more easily be understood by reading the following description of the preferred embodiments thereof taken, only by way of example, in conjunction with the accompanying drawings.